The present invention relates to the field of coarse or fine pulp screening systems, of which the purpose is to remove oversize, organic material for reprocessing.
Primary screens concentrate the oversize material into a reject stream which contains good fiber. A reject separator, then, typically recovers the good fiber from the reject stream and discharges fiber free, oversize material for reprocessing. However, the mainline pulp stream contains, also, junk (i.e., rocks, tramp material, gravel and, unwanted, organics) which, desirably, should be separated out and discharged as a unique, pulp-free flow for disposal. The aforesaid resulted in efforts to remove junk in primary screens by a centrifugal trap in an inlet chamber. However, partly due to the relatively higher, fluent consistency in this inlet chamber part of the system, this approach did not remove smaller particles, such as gravel, effectively, but it was successful mainly in removing large particles capable of jamming the primary screen. Smaller particles tended to carry over, to be discharged with the rejected, organic material.
The foregoing illustrates limitations known to exist in present devices and methods. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.